Doctor Who: Inferno (1970)

I found this to be very similar to the previous "Ambassadors of Death" series with the "Doctor" (Jon Pertwee) and his assistant "Liz" (Caroline John) recruited by the "Brigadier" (Nicholas Courtney) to help solve some mysterious goings-on at another top secret government establishment. This time, it's "Prof. Stahlman" (Olaf Pooley) who is leading a team determined to drill into the Earth's core and release an unlimited source of cheap energy. Of course, this isn't anywhere near as straightforward as it sounds and the deeper they go, the more unusual the side effects on the scientific team who are working on the project. Things become even more complicated when a power surge opens a time tear and the doctor ends up in a parallel universe where a much more militaristic government is in charg...